This invention relates generally, as indicated, to a mill liner, and more particularly, to certain improvements in the liner construction of a dry autogenous mill.
During the processing of crude iron ore and other such materials, the mined crude ore is fed to a mill where it is broken up and ground before passing through a classifier where the material is separated according to size. One such type of mill commonly used for this purpose is a dry autogenous or self-grinding mill. Both the shell and ends of such a mill are completely lined to protect the shell against wear and assist in the crushing and grinding action in the mill.
Heretofore, a common type of shell liner consisted of a series of circumferentially spaced longitudinally extending lifting rails, with separate lug members therebetween to protect the shell between the rails. The ends of the mill were also lined with radial inner and outer rows of wedge-shape deflector liner members and one or more rows of ring liner members between the outer row of deflector liner members and the ends of the shell.
The deflector liner members or elements were designed to provide a keying action in the mill to assist in the crushing and grinding action. However, in actual practice it was found that because of the substantial axial thickness of the deflector liner members, the width of the ore curtain was unduly restricted, and the operating volume of the mill was also adversely affected resulting in reduced mill performance. Also, because of the thickness of the deflector liner members, foundry practices required that such liner members be cast either in two pieces or with hollow centers to insure homogeneous metallurgy, whereby the mill ends were not always adequately protected by the liner members and began to show evidence of premature wear, despite high scrap loss on removal and replacement of the liner members. Moreover, such liner members were quite heavy, making them difficult to handle, which greatly increased the time required to change the liner members, and the amount of scrap loss was also substantial, both of which substantially added to the overall maintenance cost for the mills.
Also, for the larger mills, it was previously thought necessary in order to obtain the desired tonnage throughput of the mills to provide for some peripheral discharge of material from the mills by including a grate at the discharge end of the mills. However, in actual practice, it was found that the grate was not very effective in obtaining the desired peripheral discharge, and such grate was also subject to excessive wear.